Psoriasis is a common, chronic disease affecting greater than 2% of the population that is associated with substantial morbidity, impairment in health related quality of life and excess mortality. Numerous cross- sectional, hospital-based, or tertiary care referral-based studies have found higher rates of co-morbidities such as obesity, diabetes;hyperlipidemia, atherosclerosis, and cardiovascular disease in patients with psoriasis. Few studies however have used longitudinal, population-based methods to properly characterize the nature of these associations. It is unclear however, whether chronic psoriasis patients are directly at increased risk for developing diabetes mellitus as opposed to only having an association with diabetes through other common risk factors (i.e., confounding) or through treatment effects. For example, psoriasis is associated with obesity, which is also a major risk factor for the development of diabetes. Of note, several associated co-morbidities such as obesity also share similar pathologic abnormalities as psoriasis, suggesting biologic plausibility for a direct relationship. Moreover, emerging mechanistic data suggests that psoriasis itself could lead to an increased risk of diabetes. For example the inflammatory pathways associated with psoriasis have also been linked to insulin resistance, which could mean that the pathophysiology of psoriasis itself may lead to diabetes. Furthermore, a preliminary study suggested an association with endogenous insulin resistance in psoriatic patients. In addition, little is known about how chronic psoriasis could lead to adverse outcomes among patients with diabetes and psoriasis. The goals of this proposal are to gain the epidemiologic methods and tools to conduct high-quality epidemiologic studies as outlined in PAR-06-536 and to use these techniques to better understand the association between psoriasis and diabetes. The aims are: To determine if psoriasis patients are at increased risk of developing diabetes and the extent to which psoriasis severity and other factors such as obesity influence this risk using a cohort study;to determine the impact psoriasis has on control of diabetes based on HbA1C levels using a cohort study;and to develop the skills to perform these studies through participation in a comprehensive program of study in clinical epidemiology. Studying the relationships between psoriasis and diabetes will have important implications to our understanding of the relationship of chronic inflammatory diseases and their systemic complications and will potentially impact long term care of the over 7 million US patients with psoriasis through changes in current screening and treatment for diabetes in this population.